In many data transfer networks, there is a need to produce timing information and/or position information based on one or more satellite signals received from a satellite system. The satellite system can be a Global Navigation Satellite System “GNSS” that can be for example the US Global Positioning System “GPS”, the Russian GLONASS, the European Galileo system, or the Chinese Beidou system. When a device for producing the timing and/or position information starts up, the device needs sufficiently strong satellite signals from a sufficient number of satellites and/or assistance information which aids the device to start up with weaker satellite signals from a smaller number of satellites. The assistance information may comprise for example Assisted-GPS “A-GPS” data such as almanac data indicative of the status of the satellite constellation of the satellite system and/or ephemeris data indicative of orbital information related to one or more satellites of the satellite system. Furthermore, the assistance information may comprise position data which expresses the geographical position of the device during the start-up.
When the above-mentioned assistance information is not available, a typical requirement is to have an outdoor GNSS-antenna with a clear sky view so as to receive sufficiently strong satellite signals from a sufficient number of GNSS-satellites. A receiving GNSS-device may need many minutes to receive required data from the GNSS-satellites so as to resolve a correct location of the GNSS-device. A receiving GNSS-device adapted to produce timing information will also carry out position determination in which the GNSS-device uses at least four satellites to average the position of the device over a number of hours, usually over 24 hours, to achieve a position fix. If the GNSS-antenna is in an urban canyon or otherwise incapable of receiving sufficiently strong satellite signals from a sufficient number of satellites, the accuracy of the position fix is limited and this will show an error in the timing information. Therefore, in many cases, it is important to arrange the assistance information, e.g. the A-GPS data, to be available to the receiving GNSS-device.
The above-mentioned A-GPS data is maintained in an A-GPS server from which a GNSS-device of the kind mentioned above can retrieve the A-GPS data by using A-GPS protocols for transferring the A-GPS data. The A-GPS protocols constitute a part of a Positioning Protocol defined by two different standardization bodies: the 3rd Generation Partnership Project “3GPP” and the Open Mobile Alliance “OMA”. A typical approach to enable a GNSS-device to run the A-GPS protocols is to provide the GNSS-device with a dedicated A-GPS chip that comprises means for running the A-GPS protocols. Providing a GNSS-device with an A-GPS chip for running the A-GPS protocols would increase the complexity and the costs of the GNSS-device. The cost impact can be significant especially if a data transfer network comprises a number of GNSS-devices and each of these GNSS-devices needs to be provided with an A-GPS chip.